1. Field of the Invention
The present invention relates to a seat-occupant restraining apparatus which expands a belt for restraining a seat occupant in a seat at the time of a collision of a vehicle, the belt being expanded with a high-pressure gas supplied from an inflator.
2. Description of the Related Art
An air belt assembly which includes a bag accommodated in a seat belt so that the bag is expanded to gently restrain a seat occupant at the time of a collision of a vehicle is already known, for example, from Japanese Patent Application Laid-Open No. 6-56001.
The bag of such an air belt assembly has a vent hole, and after the bag has been expanded, the internal pressure of the bag is adjusted to an appropriate value by discharging an extra high-pressure gas through the vent hole.
However, the vent hole, which is a simple opening formed in the bag and which automatically opens in the process of expansion of the folded bag, involves the problem that if the manner of the expansion of the folded bag varies, the timing or extent of opening of the vent hole does not become constant and it becomes difficult to discharge the extra high-pressure gas at an appropriate time.
A buckle assembly, to which a tongue device that is provided on a belt is connected, is pivotally supported on a seat base to be swingable forwardly and rearwardly, in order to compensate for a variation in the angle of the belt due to the forward or rearward position of a seat or the shape of the body of the seat occupant, when the seat occupant wears the seat belt assembly. For the same reason, in the air belt assembly as well, the buckle assembly needs to be supported pivotally to be swingable forwardly and rearwardly.
FIG. 14 shows the essential portion of a conventional air belt assembly. A buckle assembly 04, to which a tongue device 03 is connected, provided at one end of each of a shoulder belt 01 and a lap belt 02, is pivotally supported on a seat base 05 by a pivot pin 06 to be swingable forwardly and rearwardly. At the time of a collision of the vehicle, the high-pressure gas, produced by an inflator 07, integrally provided on the buckle assembly 04, is supplied to the shoulder belt 01 through the buckle assembly 04 and the tongue device 03, thereby expanding the shoulder belt 01 to gently restrain the seat occupant. In such a conventional air belt assembly, since the inflator 07 is integrally provided on the buckle assembly 04, as the buckle assembly 04 pivots about the pivot pin 06, the inflator 07 integrally pivots. This leads to the problem that limitations are put on the design because it is necessary to avoid the interference of the inflator 07 with other members.
The magnitudes of the shocks due to collisions of vehicles widely range from a small shock, for which a seat occupant can be fully restrained with only a normal seat belt, to a large shock, for which it is necessary to produce the largest possible restraining force. However, in a case where a seat occupant can be fully restrained, for example, merely by operating an air belt assembly without operating an air bag assembly, if both the air bag assembly and the air belt assembly are operated at the same time, the air bag assembly, which originally need not be used, will be wastefully used and the problem of an economic burden to a user will occur.